The slope of the floor

[PlatinumZealot]

I know that you get better air flow under the car by giving the floor a rearward rake. I think this is to do with the rise in thickness of the boundary layer as air passes. So here are my poorly phrased questions:

Is the floor and other main parts of the car like the crankshaft centre line, and wing profiles etc. drawn on horizontal planes and then the ride height between front and back adjusted later to get it the floor to slope? (That is, when the car is on the track all the components tilt forward with the slope of the floor.)

OR

Is the floor designed with the slope built in? That is, when the engine and other parts of the car are horizontal the floor has a slope. Rephrasing: If the floor is the reference plane; is the rest of the car designed slanted relative to it so that when the car is on the track with the engine center line is horizontal and the front and rear wing planes at the calculated angles, the floor is at slanted?

I was looking at this picture of the Lotus and then I started thinking about it.

[czt]

It will all be designed horizontal, then your chose ride heights put the rake into the car.